UI example scrolling list Fix

[ickshonpe]

Objective

Fix for the scrolling list in the UI example.

The upgrade to Taffy 3 broke the scrolling list because in Taffy 3 Dimension::Undefined is removed and Val::Undefined is mapped to Dimension::Auto. The example was giving the list container a max height of Val::Undefined which previously in Taffy internally would have been translated to Dimension::Points(0.) but now becomes Dimension::Auto which means that instead of taking the height of its parent, the list container takes the height of its content, that is the height of the entire list. So the list widget believes that the list fits inside the container and can't be scrolled.

Fixes #8056

Solution

Set the height constraint of the list's container to zero so it doesn't automatically take the height of its content and break the list widget.

Changelog

• Changed the height constraint of the node containing the list to Val::Px(0.), so it doesn't take the height of its content and break the list widget.

[rparrett]

Fixes the issue for me. Cool that this is just a broken example.

The scrolling implementation seems slightly confusing to me. I would personally expect the "inner container" to expand to the height of the content, and for the scrolling system to be using the height of the outer container for its calculations instead.

I might look into that as a follow-up.

[rparrett]

I took a close look and it seemed simpler than I initially thought to fix up the implementation so I opened #8069 as a potential alternative.

[nicoburns]

I would personally expect the "inner container" to expand to the height of the content, and for the scrolling system to be using the height of the outer container for its calculations instead.

I would also expect this. And as such, I believe we should go with the fix in #8069 instead of this one.

[ickshonpe]

Closed in favour of #8069